標題: Relaxation dynamics and structural characterization of organic nanoparticles with enhanced emission
作者: Bhongale, CJ
Chang, CW
Lee, CS
Diau, EWG
Hsu, CS
應用化學系分子科學碩博班
Institute of Molecular science
公開日期: 21-七月-2005
摘要: With a reprecipitation method, we prepared fluorescent organic nanoparticles of 1,4-di[(E)-2-phenyl-1-propenyl]-benzene (PPB) that feature weak emission in solution but exhibit blue-shifted absorption and strong emission as aggregates. Picosecond fluorescent transients of these PPB nanoparticles showed biexponential decay, described with a consecutive kinetic model involving two emissive states. X-ray diffraction patterns of PPB nanocrystals indicate long-range packing structures of two types, one the same as in a single crystal and the other not yet determined. PPB molecules in a crystal show an arrangement of a herringbone type with three benzene rings in a PPB unit being nearly planar and two methyl groups of the unit pointing along the same direction, in contrast to the twisted structure of an isolated PPB molecule. Fluorescence transients of PPB on a femtosecond scale indicate an efficient channel for isomerization that is activated for free PPB in solution but inhibited in PPB forming nanoparticles, demonstrating the significance of molecular geometry and twisting motions that affect the relaxation dynamics in the excited state. The versatile techniques combined in this work provide strong evidence to improve our understanding of optical properties in organic nanoparticles dependent on size.
URI: http://dx.doi.org/10.1021/jp0502297
http://hdl.handle.net/11536/13478
ISSN: 1520-6106
DOI: 10.1021/jp0502297
期刊: JOURNAL OF PHYSICAL CHEMISTRY B
Volume: 109
Issue: 28
起始頁: 13472
結束頁: 13482
顯示於類別:期刊論文


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